1. The year of Profitable Growth Global network of innovation Rotor-Earth-Fault Protection

2. Power Automation 2 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Presenter:Dr. Hans-Joachim Herrmann PTD PA13 Phone +49 911 433 8266 E-Mail: Hans-Joachim.Herrmann@siemens.com Generator Protection Rotor-Earth-Fault Protection

3. Power Automation 3 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Requirement for Rotor Earth Fault Protection  in case of an earth fault, only small currents flow due to the galvanical isolation Problem: Double earth faults and interturn faults as a consequence of an earth fault cause: magnetical unbalance (unbalanced forces; violent vibration) high currents at the fault location Task: Detection an earth fault already when it starts to build up  Destruction of the Rotor (Generator) Earth fault in the rotor RERE CECE Rotor Excitation system + - Stator

4. Power Automation 4 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Protection Principle Excitation system + - Voltage Source „Earthing brush “ Coupling Unit Measuring - Incoupling of an AC voltage (50 Hz or 60 Hz) - Measuring of the earth fault current - Measuring of the earth fault resistance - Incoupling of low frequency square wave voltage Principles: Higher Sensitivity

5. Power Automation 5 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Earth Current Criterion Principle (50 Hz/60Hz - Voltage Injection)

6. Power Automation 6 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Earth Current Measurement Connection Also I EE2 at 7UM62 is possible AC Voltage Source appr. 42V or 65V Documentation for Coupling Device in the Internet www.siprotec.com External resistors at excitation voltages > 150 V (circulating current >0,2A)

7. Power Automation 7 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Gain Characteristic of the R, C, L-Circuit Imax approx. 300 mA

8. Power Automation 8 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Earth Current Criterion Protection Settings Protection with two stages: Measuring circuit supervision Z Couplingl (50Hz) = 400  Z Couplingl (60Hz) = 335  Imax ca. 100 mA (voltage source decreases a little bit ) Note: Coupling impedance only with R and C Finally setting during commissioning

9. Power Automation 9 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Earth Current Criterion Logic

10. Power Automation 10 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Calculation of the Fault Resistance R E (50Hz/60Hz- Voltage Injection) 100V42V u Digital protection (7UM62) calculation of R E RERE CECE RVRV CKCK RVRV CKCK L1L2L3 i L 1) 1) Recommended at static excitation with inject harmonics (3rd harm.; 6th harm.)

11. Power Automation 11 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Calculation Formula of the Fault Resistance R E (1) (2) (3) (4) combining (3) and (4): Note: R V * and X K * are measured during commissioning Model : Z ers Z Mess Z X* K R* V XEXE RERE

12. Power Automation 12 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Earth Fault Resistance Calculation Logic

13. Power Automation 13 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Earth Fault Resistance Calculation Settings Measured during commissioning Measuring circuit supervision Measured current can be influenced by disturbances Correction during primary test, (in most case the alarm stage is concerned)

14. Power Automation 14 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Injection of Square Wave Voltage with Low Frequency Basic Diagram Excitation + - CECE RERE Digital Protection (7UM62) UHUH RVRV RVRV U control U meas. RMRM 7XR6004 Controlling device (7XT71) IEIE Measuring transducer R E Fault resistance R V Coupling resistor U H Auxiliary supply (  50V) R M Measuring shunt resistor C E Rotor capacitance Typical frequency: 1 - 3 Hz

15. Power Automation 15 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Injection of Square Wave Voltage Connection Diagram (7UM62)

16. Power Automation 16 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Injection of Square Wave Voltage with Low Frequency Basic Principle RV2RV2 RERE CECE UHUH UMUM RMRM UHUH UMUM UMUM 50V - 50V 1,88V - 1,88V 0,75V - 0,75V t t t iEiE Equivalent circuit:

17. Power Automation 17 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Sources of Error and Error Compensation Influence of field voltage and earth fault location a) Earth fault location Shifting of measuring voltage with a positive or negative dc voltage b) Jumps in the field voltage a change in the field voltage takes to jumps in the dc-voltage shifting U dc = dc voltage shifting Solution: Calculation of the difference voltage  U = |U M1 - U M2 |  U 1 = |U M1 - U M2 |  U 3 = |U M3 - U M4 |  U 2 = |U M2 - U M3 | Solution: Block of measuring at jumps (e.g.  U 1 =  U 2 ) UMUM U dc U dc1 U M1 U M2 U M3 U M4 U M1 U M2 U dc2 UMUM

18. Power Automation 18 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Calculation Formulas RERE CECE UHUH UMUM RMRM RV2RV2 UMUM U1U1 U2U2 Algorithm Voltage divider: Filtering: Amplitude-log frequency curve : f A = 800 Hz; N = 64 03060 90 120 150 180 210 240 270 300 0.001 0.01 0.1 1 f in Hz G(f) Continuity supervision: Validity requirement otherwise

19. Power Automation 19 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Logic Diagram Rotor Earth Fault Protection (1-3Hz)

20. Power Automation 20 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Rotor Earth Fault Protection (1-3Hz) Setting Values Measuring circuit supervision If the integrated test function is used, pick-up value of test resistor Advanced parameter only visible in DIGSI

21. Power Automation 21 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Connection of the Rotor Earth Fault Protection G RW RERE CECE EM EX-T L+ RW UGUG RERE CECE L- (50/60 Hz) (1 - 3 Hz) (50/60 Hz) (1 - 3 Hz) 40k  4µF a) rotating diodes b) separate Exciter (static excitation) 40k 

22. Power Automation 22 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Generator with Rotating Excitation Fault Free Condition (Square Wave Principle) Chance of charge of rotor earth capacitance Disturbances by the excitation generator

23. Power Automation 23 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Generator with Rotating Excitation Test Condition with a Fault Resistor Fault resistor is inverse proportional to the difference voltage

24. Power Automation 24 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Parallel Operation of Rotor Earth Fault Protections 100V42V C K ;4µF R K ;105  R V ;40k  RERE 7UM62 u Control u Meas. i REF u REF 7UM61 nur i REF or 1- 3 Hz principle 50 Hz principle

25. Power Automation 25 Power Transmission and Distribution Power Automation Progress. It‘s that simple. Parallel Operation of Rotor Earth Fault Protections Measurement with the 50/60 Hz Principle Measurement 7UM61 or 7UM62 (R V is earthed for an AC voltage) Equivalent circuit: seen from the 7UM6, R V already is interpreted as a rotor-to-earth resistance Measurement: measured as a fault resistance Case 1: Case 2: alarm stage becomes less sensitive  open brushes can not be find out

26. Power Automation 26 Power Transmission and Distribution Power Automation Progress. It‘s that simple. RV2RV2 RERE RMRM 2C K (8µF) U meas U2U2 Measurement 7UM62 (1- 3 Hz) (C K is earthed for a DC voltage ) Equivalent circuit:  seen from the 7UM6: high rotor capacitance  capacitors will not be completely loaded   U ~ R E -1 under no-earth-fault conditions a fault resistance is already measured  alarm stage becomes less sensitive (approx. 50k  )  longer measuring time Parallel Operation of Rotor Earth Fault Protections Measurement with the Square Wave Principle